This.
It's not going to be an option, and we're going to hit the point where they'll need to start deleting expansion items from the game to make room for new ones.
Remember that chest piece appearance you're so fond of? Better not get too attached to it...
Even if, logistics-wise, that's what they'd be doing, the story, setting, and content of this game are still very much loved by the community.
We're not talking about rebuilding the ENTIRE game from scratch, just about updating database and netcode.
Again, they built 2.0 WHILE maintaining and updating 1.0, and that required rebuilding nearly everything except some parts of major cities, since the old world was built from copy-pasta.